1. Field of the Invention
The present invention relates to a dispenser for a liquid crystal display panel and a dispensing method using the same, and more particularly, to a dispenser for a liquid crystal display panel and its dispensing method using the dispenser to control a gap between a large-sized substrate and a nozzle, or to align nozzles.
2. Discussion of the Related Art
In general, a liquid crystal display panel is a display device where data signals according to picture information are individually supplied to liquid crystal cells arranged in a matrix form. Light transmittance of the liquid crystal cells is controlled to display a desired picture according to the picture information. The liquid crystal display device includes a liquid crystal display panel in which the liquid crystal cells are arranged in a matrix form, and a driver integrated circuit (IC) for driving the liquid crystal cells. More particularly, the liquid crystal display panel includes a color filter substrate and a thin film transistor array substrate attached to each other. The liquid crystal display panel further includes a liquid crystal layer in between the color filter substrate and the thin film transistor array substrate.
Data lines and gate lines are formed on the thin film transistor array substrate of the liquid crystal display panel, to cross at right angles, thereby defining liquid crystal cells at every crossing. The data lines transmit a data signal supplied from the data driver integrated circuit to the liquid crystal cells, and the gate lines transmit a scan signal supplied from the gate driver integrated circuit to the liquid crystal cells. At one end portion of each of the data lines and gate lines, a data pad and a gate pad are provided in which data signals and scan signals are applied from the data driver integrated circuit and the gate driver integrated circuit. The gate driver integrated circuit sequentially supplies the scan signal to the gate lines so that the liquid crystal cells arranged in the matrix form can be sequentially selected one line by one line while a data signal is supplied to the selected one line of the liquid crystal cells from the data driver integrated circuit.
A common electrode and a pixel electrode are respectively formed on the inner opposing sides of the color filter substrate and the thin film transistor array substrate such that an electric field can be applied to the liquid crystal layer. The pixel electrode is formed in each liquid crystal cell on the thin film transistor array substrate, while the common electrode is integrally formed across the entire surface of the color filter substrate. By controlling a voltage applied to the pixel electrode in a state where a voltage is applied to the common electrode, light transmittance of each liquid crystal cells can be individually controlled.
To control the voltage applied to the pixel electrode by liquid crystal cells, a thin film transistor is used as a switching device in each liquid crystal cell. Other elements of the liquid crystal display device will now be describe in reference to FIG. 1, which is a plane view of the unit liquid crystal display panel formed by a thin film transistor array substrate and a color filter substrate according to the related art. As shown in FIG. 1, the liquid crystal display panel 100 includes an image display part 113 where the liquid crystal cells are arranged in a matrix form, a gate pad part 114 connected to the gate lines of the image display part 113, and a data pad part 115 connected to the data lines of the image display part 113. The gate pad part 114 and the data pad part 115 are formed along an edge region of the thin film transistor array substrate 101 which does not overlap with the color filter substrate 102. The gate pad part 114 supplies a scan signal from the gate driver integrated circuit to the gate lines of the image display part 113. The data pad part 115 supplies image information from the data driver integrated circuit to the data lines of the image display part 113.
Data lines to which image information is applied and gate lines to which a scan signal is applied are provided on the thin film transistor array substrate 101. The data lines and the gate lines cross each other. Additionally, a thin film transistor for switching the liquid crystal cells is provided at the crossing of the data lines and the gate lines. A pixel electrode for driving the liquid crystal cells is connected to the thin film transistor and provided on the thin film transistor array substrate 101. A passivation film for protecting the pixel electrode and the thin film transistor is formed over the entire surface of the thin film transistor array substrate 101.
Color filters separately coated in each of the cell regions are separated by a black matrix on the color filter substrate 102. In addition, a common transparent electrode is provided on the color filter substrate 102. The thin film transistor array substrate 101 and the color filter substrate 102 are separated by a cell gap. The cell gap is maintained by a spacer between the thin film transistor array substrate 101 and the color filter substrate 102, which are attached by a seal pattern 116 formed along an outer edge of the image display part 113, thereby forming a unit liquid crystal display panel.
In fabricating a unit liquid crystal display panel, a method for simultaneously forming a plurality of unit liquid crystal display panels on a large-scale mother substrate is typically used. This method requires a process for separating the unit liquid crystal display panels from the large-scale mother substrate. Subsequently, a unit liquid crystal display panel separated from the large-scale mother substrate has liquid crystal is injected through a liquid crystal injection opening to form a liquid crystal layer in the cell-gap which separates the thin film transistor array substrate 101 and the color filter substrate 102. Then the liquid crystal injection opening is sealed.
To fabricate a unit liquid crystal display panel, thee following processes are generally required: the thin film transistor array substrate 101 and the color filter substrate 102 are separately fabricated on first and second mother substrates; the first and second mother substrates are attached such that a uniform cell-gap is maintained therebetween; the attached first and second mother substrates are cut into unit panels; and then liquid crystal is injected into the cell-gap between the thin film transistor array substrate 101 and the color filter substrate 102. A process of forming the seal pattern 116 along an outer edge of the image display part 113 is required to attach the thin film transistor array substrate 101 and the color filter substrate 102. The related art method of seal pattern forming will now be described.
FIGS. 2A and 2B illustrate a screen printing method to form a seal pattern according to the related art. As shown in FIGS. 2A and 2B, a screen mask 206 is patterned so that a seal pattern forming region is selectively exposed. Then, a rubber squeegee 208 for selectively supplying a sealant 203 to the substrate 200 through the screen mask 206 is used to draw the sealant to form the seal patterns 216A˜216C to prevent leakage of liquid crystal. The seal patterns 216A˜216C formed on the substrate 200 have a gap in which liquid crystal is injected. Thus, the seal patterns 216A˜216C are formed along an outer edge of the image display parts 213A˜213C of the substrate 200 and liquid crystal injection openings 204A˜204C are formed at one side of the seal patterns 216A˜216C.
The screen printing method includes: applying the sealant 203 on the screen mask 206 with a seal pattern forming region patterned thereon; forming the seal patterns 216A˜216C on the substrate 200 through printing with the rubber squeegee 208; drying the seal patterns 216A˜216C by evaporating a solvent contained in the seal patterns 216A˜216C; and leveling it. The screen printing method is widely used because of its advantage of convenience in process. However, it is disadvantageous in that much sealant 203 is consumed since the sealant 203 is applied across the entire surface of the screen mask 206 and printed with the rubber squeegee 208 to form the seal patterns 216A˜216C. The excess sealant is wasted. In addition, the screen printing method has another disadvantage in that a rubbed orientation film (not shown) formed on the substrate 200 is degraded as a result of the screen mask 206 being brought into contact with the substrate 200. The degradation of the rubbed orientation film degrades picture quality of the liquid crystal display device. Therefore, to overcome the shortcomings of the screen printing method, a seal dispensing method has been proposed.
FIG. 3 is an exemplary view of a dispensing method for forming a seal pattern. As shown in FIG. 3, while a table 310 with the substrate 300 loaded thereon is being moved in forward/backward and left/right directions, a plurality of seal patterns 316A˜316C are simultaneously formed along an outer edge of the image display parts 313A˜313C of the substrate 300 by applying a certain pressure to sealant within a plurality of syringes 301A˜301C. In the seal dispensing method, as the sealant is selectively supplied only to the region where the seal patterns 316A˜316C are to be formed, sealant consumption is reduced compared to the screen printing method. In addition, since the syringes 301A˜301C are not in contact with orientation films (not shown) of the image display parts 313A˜313C of the substrate 300, the rubbed orientation film will not be damaged and thus a picture quality of the liquid crystal display device will not be degraded.
In the case of simultaneously forming the seal patterns 316A˜316C on the substrate 300 loaded on the table 310 by using the plurality of syringes 301A˜301C, a technique for precisely aligning the plural syringes 301A˜301C and a technique for precisely controlling a gap between the substrate 300 and the syringes 301A˜301C are required. That is, if the plural syringes 301A˜301C are not properly aligned, the plural seal patterns 316A˜316C may be formed rather within the image display parts 313A˜313C rather than being formed along the outer edge of the image display parts 313A˜313C, which would result in a defective liquid crystal display panel. In addition, if the substrate 300 and the syringes 301A˜301C are too close to the substrate 300 or have narrower gap than the desired gap, the seal patterns 316A˜316C formed on the substrate 300 are formed too wide and too low. If, however, the substrate 300 and the syringes 301A˜301C are too far from the substrate 300 or have a wider gap than the desired gap, the seal patterns 316A˜316C formed on the substrate 300 are formed too narrow and too high.
In the related art, a dummy substrate is used to align the plural syringes 301A˜301C and to adjust the gap between the substrate 300 and the syringes 301A˜301C, which will now be described with reference to FIG. 4, which is an exemplary view showing a seal dispenser of a liquid crystal display panel in accordance with the related art. As shown in FIG. 4, the related art seal dispenser includes: a dummy substrate 401 loaded on a table 400; a plurality of syringes 402A˜402C filled with a sealant; nozzles 403A˜403C provided at one end portion of the syringes 402A˜402C and supplying the sealant onto the dummy substrate 401; and image cameras 404A˜404C respectively provided at the side of the syringes 403A˜403C.
First, in order to adjust the gap between the dummy substrate 401 and the syringes 402A˜402C, the syringes 402A˜402C are sequentially lowered so that the nozzles 403A˜403C just come into contact with the surface of the dummy substrate 401. Then, the nozzles 403A˜403C are raised to a predetermined height above the surface of the dummy substrate 401 to thereby obtaining a desired gap between the dummy substrate 401 and the syringes 402A˜402C. To align the syringes 402A˜402C, the sealant is applied on the dummy substrate 401 through the nozzles 403A˜403C to form a vertically crossing seal pattern, and then an image of the seal pattern is detected with the image cameras 404A˜404C provided at the syringes 402A˜402C to check the alignment state and the position of the syringes 402A˜402C is compensated. After the dummy substrate 401 and the syringes 402A˜402C are adjusted to have a desired gap therebetween and the syringes 402A˜402C are aligned, the dummy substrate 401 is unloaded and a substrate on which a seal pattern is to be formed is loaded on the table 400 and a seal pattern is formed on the substrate.
As the size of liquid crystal display panel increase, the area of the substrate used to fabricate a liquid crystal display panel increases. The size of a substrate for fabricating the liquid crystal display panel is practically the same as the dummy substrate 401 except that the former is used for actually fabricating a liquid crystal display panel. Loading and unloading of the dummy substrate 401 are performed manually by an operator. Thus, if the size of the dummy substrate 401 is large, it is very difficult to load and unload the dummy substrate 401, causing a delay in the process and thus degrading productivity. In addition, manually loading and unloading the dummy substrate 401 increases the chances that a dummy substrate may be damaged, which increases fabrication cost. Moreover, since space is required for the operator to perform the loading and unloading of the dummy substrate 401, a space efficiency of a clean room is degraded and thus facility expense is increased.